A big band or jazz orchestra is a type of musical ensemble of jazz music that usually consists of ten or more musicians with four sections: saxophones, trumpets, trombones, and a rhythm section. Big bands originated during the early 1910s and dominated jazz in the early 1940s when swing was most popular. The term "big band" is also used to describe a genre of music, although this was not the only style of music played by big bands.
Big bands started as accompaniment for dancing the Lindy Hop. In contrast to the typical jazz emphasis on improvisation, big bands relied on written compositions and arrangements. They gave a greater role to bandleaders, arrangers, and sections of instruments rather than soloists.
Big bands generally have four sections: trumpets, trombones, saxophones, and a rhythm section of guitar, piano, double bass, and drums. The division in early big bands, from the 1920s to 1930s, was typically two or three trumpets, one or two trombones, three or four saxophones, and a rhythm section of four instruments. In the 1940s, Stan Kenton's band used up to five trumpets, five trombones (three tenor and two bass trombones), five saxophones (two alto saxophones, two tenor saxophones, one baritone saxophone), and a rhythm section. Duke Ellington at one time used six trumpets. While most big bands dropped the previously common jazz clarinet from their arrangements (other than the clarinet-led orchestras of Artie Shaw and Benny Goodman), many Duke Ellington songs had clarinet parts, often replacing or doubling one of the tenor saxophone parts; more rarely, Ellington would substitute baritone sax for bass clarinet, such as in "Ase's Death" from Swinging Suites. Boyd Raeburn drew from symphony orchestras by adding flute, French horn, strings, and timpani to his band. In the late 1930s, Shep Fields incorporated a solo accordion, temple blocks, piccolo, violins and a viola into his Rippling Rhythm Orchestra. Paul Whiteman also featured a solo accordion in his ensemble.